<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
</head>

<body>
    <div id="app">
        <!-- wacth可以监听一个fata属性或者一个计算属性，就会触发watch侦听的回调函数
            可以在回调函数做后续事情
        -->
        <input type="text" v-model="msg">
        <button @click="count++">累加</button>
        doubleCount:{{doubleCount}}
    </div>
    <script>
        Vue.config.productionTip = false;
        
        const vm = new Vue({
            el: "#app",
            data() {
                return {
                   msg:"", 
                   count:2,
                };
            },
            computed:{
                doubleCount(){
                    return this.count*2;
                }
            },
            watch:{
                msg(){
                    console.log("监听");
                },
                doubleCount(){
                    console.log("重新计算了Count");
                }
            }
        })
</script>
</body>

</html>